The proposed research is directed at encoding processes in the cochlear nuclei for complex sound waveforms introduced acoustically and electrically. While anatomical and electrophysiological observations have indicated structural and functional unit classifications within the cochlear nuclei, no systematic investigation of their responses to more complicated stimuli has been made. This work will use established histological and electrophysiological criteria to identify cellular loci and characteristics and then investigate their responses to signals containing more than one frequency component, i.e., complex stimuli. In addition, to the introduction of acoustic signals to gain more understanding of the normal function of these neurons, some preparations will use electrically introduced waveforms to determine the difference between activity induced by sound and by a cochlear prosthesis. Guinea pigs acutely anesthetized with ketamine and zylazine will provide the usual preparation, but responses will also be observed in some instances using decerbrate preparations to evaluate anesthetic effects. These experiments will determine the transfer of information from stimulus waveforms into unit activity within the subdivisions of the cochlear nuclei for both acoustic and electrical inputs. By using coordinated techniques in a well controlled animal preparation, the procedures for optimizing the information presented to humans with partial to total hearing loss can be examined.